In the prior art, a so-called full-open type can lid is widely employed as a can lid of a can which needs to have a wide opening to take out contents, such as a canned fruit, a canned fish, a canned beef, a canned vegetables and so on. According to the full-open type can lid, an opening piece is enclosed by a score line drawn along a periphery of a panel portion of a can lid, and a tab for rupturing the score line to take out the contents is fixed on the opening piece.
As a conventional art of this kind of full-open type can lid, Japanese Patent Laid-Opens No. 2-180148 and No. 2-502814 disclose techniques to form a multilayered folded portion covering an edge of a ruptured score line, for the purpose of preventing a hand or fingers of a can opener to be injured by a broken edge of the opening piece or an edge of the ruptured score line at an opening operation of the can or when taking out the contents from the can.
However, according to the vessel lid with a safe opening edge taught by Japanese Patent Laid-Open No. 2-180148, folded portions are situated across the score line to cover an opening edge of the score line. Therefore, the opening edge will be contacted with the folded portion when opening the can, otherwise, the folded portions will be contacted to interfere with each other. For this reason, an excessive force is required to open the can lid and this deteriorates an openability of the can.
Meanwhile, according to the can lid taught by Japanese Patent Laid-Open No. 2-502814, although a leading edge of the folded portion is not situated across the score line, a clearance between a surface where the score line is drawn and an outer folded portion is maintained widely as illustrated therein. For this reason, stiffness in the vicinity of a panel portion is insufficient and the openability thereof is also less than perfect. Additionally, clearances between each layers of an inner folded portion are narrowed. This makes a forming of the folded portion difficult and deteriorates a quality of an inner surface of the can lid.